[aes,dv] Add coverage bins and crosses for AES-GCM

This commit adds coverage bins and crosses for different
AAD and TEXT lengths. The bins cover multiple blocks
and partial block lengths as well as cipher operations (enc,dec).

Signed-off-by: Pascal Nasahl <[email protected]>

hw/ip/aes/dv/cov/aes_cov_if.sv

@@ -282,6 +282,79 @@ interface aes_cov_if
       }
   endgroup // aes_reg_interleave_cg
 
+  covergroup aes_gcm_text_len_cg  with function sample(
+             int                              text_blocks,
+             int                              text_last_block_len,
+             bit [aes_pkg::AES_OP_WIDTH-1:0]  aes_op
+             );
+    option.per_instance = 1;
+    option.name         = "aes_gcm_text_len_cg";
+
+    cp_operation: coverpoint aes_op
+      {
+        bins enc     = {AES_ENC};
+        bins dec     = {AES_DEC};
+      }
+
+    cp_text_blocks: coverpoint text_blocks
+      {
+        bins text_blocks_0    = {0};
+        bins text_blocks_l[2] = {[1:2]};
+        bins text_blocks_h    = {[3:$]};
+      }
+
+    cp_text_last_block_len: coverpoint text_last_block_len
+      {
+        bins text_last_block_len_l[2] = {[0:1]};
+        bins text_last_block_len_m[2] = {[2:13]};
+        bins text_last_block_len_h[2] = {[14:15]};
+      }
+
+    // Cross coverage points
+    // Ignore zero block in cross coverage.
+    cr_op_aad_block_len: cross cp_operation, cp_text_blocks, cp_text_last_block_len
+      {
+        ignore_bins zero_blocks = binsof(cp_text_blocks) intersect {0};
+      }
+
+  endgroup // aes_gcm_text_len_cg
+
+  covergroup aes_gcm_aad_len_cg  with function sample(
+             int                              aad_blocks,
+             int                              aad_last_block_len,
+             bit [aes_pkg::AES_OP_WIDTH-1:0]  aes_op
+             );
+    option.per_instance = 1;
+    option.name         = "aes_gcm_aad_len_cg";
+
+    cp_operation: coverpoint aes_op
+      {
+        bins enc     = {AES_ENC};
+        bins dec     = {AES_DEC};
+      }
+
+    cp_aad_blocks: coverpoint aad_blocks
+      {
+        bins aad_blocks_0    = {0};
+        bins aad_blocks_l[2] = {[1:2]};
+        bins aad_blocks_h    = {[3:$]};
+      }
+
+    cp_aad_last_block_len: coverpoint aad_last_block_len
+      {
+        bins aad_last_block_len_l[2] = {[0:1]};
+        bins aad_last_block_len_m[2] = {[2:13]};
+        bins aad_last_block_len_h[2] = {[14:15]};
+      }
+
+    // Cross coverage points
+    // Ignore zero block in cross coverage.
+    cr_op_aad_block_len: cross cp_operation, cp_aad_blocks, cp_aad_last_block_len
+      {
+        ignore_bins zero_blocks = binsof(cp_aad_blocks) intersect {0};
+      }
+
+  endgroup // aes_gcm_aad_len_cg
 
   ///////////////////////////////////
   // Instantiation Macros          //
@@ -296,7 +369,8 @@ interface aes_cov_if
  `DV_FCOV_INSTANTIATE_CG(aes_iv_interleave_cg, en_full_cov)
  `DV_FCOV_INSTANTIATE_CG(aes_key_interleave_cg, en_full_cov)
  `DV_FCOV_INSTANTIATE_CG(aes_reg_interleave_cg, en_full_cov)
-
+ `DV_FCOV_INSTANTIATE_CG(aes_gcm_text_len_cg, en_full_cov)
+ `DV_FCOV_INSTANTIATE_CG(aes_gcm_aad_len_cg, en_full_cov)
 
   ///////////////////////////////////
   // Sample functions              //
@@ -356,4 +430,18 @@ interface aes_cov_if
     aes_key_interleave_cg_inst.sample(key, idle_i);
     aes_reg_interleave_cg_inst.sample(1);
   endfunction
+
+  function automatic void cg_gcm_text_len_sample(
+           int                              text_blocks,
+           int                              text_last_block_len,
+           bit [aes_pkg::AES_OP_WIDTH-1:0]  aes_op);
+    aes_gcm_text_len_cg_inst.sample(text_blocks, text_last_block_len, aes_op);
+  endfunction
+
+  function automatic void cg_gcm_aad_len_sample(
+           int                              aad_blocks,
+           int                              aad_last_block_len,
+           bit [aes_pkg::AES_OP_WIDTH-1:0]  aes_op);
+    aes_gcm_aad_len_cg_inst.sample(aad_blocks, aad_last_block_len, aes_op);
+  endfunction
 endinterface

hw/ip/aes/dv/env/aes_scoreboard.sv

@@ -136,7 +136,25 @@ class aes_scoreboard extends cip_base_scoreboard #(
       if (keyname == csr_name && (|datain_rdy || input_item.manual_op)) begin
         input_item.data_in[i]     = wdata;
         input_item.data_in_vld[i] = 1'b1;
-        cov_if.cg_wr_data_sample(i);
+        if (input_item.mode == AES_GCM && input_item.item_type == AES_GCM_TAG) begin
+          bit [31:0] endianess_swapped = {<<8{wdata}};
+          int len_bytes = endianess_swapped / 8;
+          int blocks = len_bytes / 16;
+          int last_block_len_bytes = len_bytes % 16;
+          // In AES-GCM, len(aad) || len(data) is a 128-bit value where 64-bit
+          // each are reserved for len(aad) and len(data). Note that len(data)
+          // and len(aad) is the length in bits. To simplify the scoreboard, just
+          // take the lower 32-bits for the length. This is fine as, with 32-bit,
+          // we can represent long AADs and texts. Currently, in the DV tests,
+          // the longest AAD and text is 1023 bytes (8184 bits).
+          if (i == 3) begin
+            cov_if.cg_gcm_text_len_sample(blocks, last_block_len_bytes, input_item.operation);
+          end else if (i == 1) begin
+            cov_if.cg_gcm_aad_len_sample(blocks, last_block_len_bytes, input_item.operation);
+          end
+        end else begin
+          cov_if.cg_wr_data_sample(i);
+        end
         datain_rdy[i] = 0;
       end
     end